I am not referring to research done 10 years ago but to research done this year. There are EU rules regulating how much is allowed in these products be it e.g. cornflake and popcorn cardboard packets, paper plates etc., but researchers from quite a few European countries have tested many kinds of packaging made from recycled cardboard and paper and they all find the levels are too high. If it can leach into food why would it not leach into my soil? I don’t know what PAS100 is so cannot comment on that.
As cardboard is so widely used I thought I’d mention it, what people want to do about using it in their gardens is of course up to them.